1. Field of the Invention
This invention relates to a photoelectric focus detecting device of which the driving mechanism can be simplified and to a photographing apparatus provided with such device.
2. Related Background Art
Photographic cameras and video cameras having an automatic focus detecting device incorporated therein are commonplace, and such focus detecting device is mounted on a camera body or is incorporated in an interchangeable lens. On the other hand, the tendency of cameras and lenses toward compactness is well known and along therewith, it is required to make the detecting device compact and simplify the driving mechanism thereof.
As is well known, the automatic focus detecting system is broadly divided into the passive type and the active type. In a typical system of the passive type, photosensor arrays are disposed on two optic axes, respectively, and the correlation between an image signal obtained by driving a pivotable mirror provided on one of the optic axes and scanning the array thereon by the image of an object or by electrically scanning the array and other image signal is taken and the object distance is detected from the scanning angle thereof or the scanning distance thereof. Also, in a system of the active type, an invisible light or the like is projected from one lens side onto an object and the reflected light from the object is received by the remaining lens and directed to a photoelectric element, and in that case, at least one of a light source, a photoelectric element, a projecting lens and a light-receiving lens is moved and scanned.
In both of these types, except a few examples in which the array is electrically scanned, some driving mechanism is required and moreover, reciprocal pivotal movement and movement in a direction perpendicular to the photographing optic axis are effected and therefore, converting means such as a cam or an encoder need be provided in a connecting structure for connecting the movement of those movable elements and the movement of the focusing lens of the photo-taking optical system in the direction of the optic axis. Such connecting structure is liable to cause a reduction in accuracy.